From the prior art, work pallets of various types (i.e. a target object) for holding a workpiece to be supplied to machining processing, and work pallet positioning and fixing devices of various types for positioning such a work pallet and for fixing it to a base member have been widely supplied for practical use.
For example, in the object positioning and fixing device described in Patent Document #1, a reference seating surface for positioning in the vertical direction is formed on the upper surface of a base member, and first and second reference members for positioning in the horizontal direction are provided at locations in the vicinity of a pair of corner portions of the base member that are in a diagonal relationship. Each of the first and second reference members comprises a flange portion that is received in a fitting aperture in the base member and is fixed by a plurality of bolts, an engagement projection that projects upward from the central portion of this flange portion, a tapered engagement surface that is formed on the external peripheral surface of the engagement projection, and a bolt hole that is formed in the engagement projection.
Bolt insertion holes are formed in the work pallet at positions corresponding to the first and second reference members, and head portion reception apertures are formed at the upper portions of the bolt insertion holes for receiving bolt head portions. Annular engagement members that can be engaged in a tightly contacting state to the respective engagement projections of the first and second reference members are fixed in recessed fitting apertures that are provided in the bottom side portion of the work pallet.
The work pallet is mounted on the base member, and, in the state in which the lower surface of the work pallet is seated on the reference seating surface, the portions of the work pallet in the neighborhood of the pair of corner portions thereof are positioned and fixed in the vertical direction and in the horizontal direction on the base member by bolts being inserted through the pair of insertion holes from above and being screwingly engaged into the bolt holes of the first and second reference members.
Moreover, along with two bolt holes being formed in the other pair of corner portions of the base member that are in a diagonal relationship than the abovementioned pair of corner portions thereof, also a pair of bolt insertion holes corresponding to this pair of bolt holes are formed in the work pallet, and the portions of the work pallet in the vicinity of this other pair of corner portions thereof are fixed to the base member by screwingly inserting a pair of bolts that have been inserted through this pair of bolt insertion holes from above into the corresponding bolt holes.    Patent Document #1: JP Laid-Open Patent Publication 2011-251376